1. Field of the Invention
The present invention relates to a vibrating gyroscope which can be used for a navigation system that provides navigational guidance by detecting a rotational angular velocity to detect the position of a moving object, or used for an anti-vibration system, such as a camera-shake prevention apparatus, that prevents the adverse effects of shaking by detecting a rotational angular velocity due to external vibration, such as camera shake.
2. Description of the Related Art
FIG. 1 is a perspective view of an essential portion of an example of a conventional vibrating gyroscope, and FIG. 2 is a front view thereof. As shown in FIGS. 1 and 2, a conventional vibrating gyroscope has a vibrator portion 71. The vibrator portion 71 includes a vibrating body 73 made of a permanently elastic metal generally in the form of a regular triangular prism. Piezoelectric elements 75a, 75b, 75c, each of which is a thin and generally rectangular member, are bonded to central portions of side surfaces of the vibrating body 73 with an adhesive. Of these piezoelectric elements, the piezoelectric elements 75a, 75b are used for driving and detection while the piezoelectric element 75c is used for feedback. A drive circuit (not shown in FIGS. 1 and 2) consisting of an oscillation circuit and a phase circuit is connected across the piezoelectric elements 75a, 75b and the piezoelectric element 75c as a feedback loop for causing self-excited vibration of the vibrating body 73. A detection circuit formed of a differential amplifier, etc. is connected to the piezoelectric elements 75a, 75b.
Two supporting members 77, each of which is a generally square-bottomed U-shaped member formed of a wire rod having a high elastic modulus, are fixed on the ridge line of the vibrating body 73 between the driving and detecting piezoelectric elements 75a and 75b and in the vicinity of nodal points of the vibrating body 73. Ends of the supporting members 77 are fixed to one major surface of a generally rectangular mount base plate 79 made of a glass-epoxy material or the like.
In the vibrating gyroscope, if a drive signal is applied across the feedback piezoelectric element 75c and the driving and detecting piezoelectric elements 75a, 75b, the vibrating body 73 vibrates under a bending mode in a direction perpendicular to the surface on which the feedback piezoelectric element 75c is formed. In the case where the vibrating body 73 is rotated, the direction of vibration of the vibrating body 73 is changed by the Coriolis force so that a difference is caused between the outputs from the piezoelectric elements 75a, 75b in response to the rotational angular velocity. This output difference is processed by signal processing in the detection circuit to detect the rotational angular velocity.
The conventional vibrating gyroscope has the drawback that the vibrating characteristics of the vibrating gyroscope may change or drift in response to the change of the ambient atmosphere. This is because the piezoelectric elements detect a stress other than the Coriolis force due to the differences of the thermal expansion coefficients among the vibrating member, the piezoelectric elements and the adhesive.